Test setup / teardown - easy to add?

I have some existing assessments that use test setup, but I notice that the grading code disallows these at the moment:

https://github.com/data-8/Gofer-Grader/blob/master/gofer/ok.py#L126

Is there some structural reason for this?  How difficult would it be to add support for these?   (I'm happy to work on it, if it's feasible).